Currently, intravascular treatments such as those using catheter have been known as less-invasive treatment methods for intravascular lesions such as aneurysm. The embolization coil used for placement at a targeted site such as blood vessel or aneurysm in these intravascular treatment methods needs to show various characteristics such as those shown below.
First, the embolization coil should be flexible enough and show replacement efficiency in placement operation without damage by excessive load applied to the application site.
The embolization coil may be withdrawn and modified positionally and relocated after placement, and the embolization coil should have a function to prevent elongation then to the degree of more than its yielding point.
Various developments had been made to obtain these characteristics.
Examples of the developments include improvement of the placement efficiency of the embolization coil allowing rapid bending thereof when connected to the vascular wall, which is made possible by making the terminal of the embolization coil more flexible than the middle region, as disclosed in Patent Document 1, and provision of a function to prevent unlimited elongation of the embolization coil itself, which is made possible by installing an elongation-preventing member in the embolization coil, as disclosed in Patent Document 2.
However, even with such traditional technologies, there were still many problems to be studied, for example, for prevention of breakage of the elongation-preventing member (e.g., prevention of breakage when the coil is wound into a shape with a smaller diameter) and for improvement of the delivery efficiency of the embolization coil (efficiency in relocation of embolization coil in catheter and also in positional correction and relocation after withdrawal).